McKennon was an avid Oregon Trail historian. He worked at the Oregon Trail Interpretive Center giving instructional speeches and put together songs, stories and informational documents leading up the Oregon Trail's sesquicentennial (150th anniversary).

He also worked with OPB (Oregon Public Broadcasting) creating "The Pappenheimers", an instructional video series to help teach children German. His character lived in Volkswagen Bus and would tell stories about relatives in Germany. Many of the episodes had clips of Germany as well as cartoons.

He is also known for his recording of an insane laugh, used for the Hyena character in Lady and the Tramp, and later the villain, Ripper Roo in the Crash Bandicoot video games.

McKennon married his childhood sweetheart, Betty Warner, in Portland, Oregon in 1942, a marriage lasting until his death in 2009. The couple had six daughters and two sons. They lived in California until 1968, when they moved to Cannon Beach, Oregon, from where Dallas commuted for acting and voiceover roles. McKennon died of natural causes on July 14, 2009 at the Willapa Harbor Care Center in Raymond, Washington five days before his 90th birthday.[3]